The invention relates to self-expanding stent delivery systems, which are used to implant a stent into a patient""s body lumen to maintain the patency thereof. The stent delivery system is useful in the treatment and repair of body lumens, including coronary arteries, renal arteries, carotid arteries, and other body lumens.
Stents are generally cylindrically-shaped devices which function to hold open and sometimes expand a segment of a blood vessel or other body lumen. They are particularly suitable for use to support and hold back a dissected arterial lining which can occlude the fluid passageway therethrough. Stents also are useful in maintaining the patency of a body lumen, such as a coronary artery, after a percutaneous transluminal coronary angioplasty (PTCA) procedure or an atherectomy procedure to open a stenosed area of the artery.
A variety of devices are known in the art for use as stents and have included coiled wires in a variety of patterns that are expanded after being placed intraluminally by a balloon catheter; helically wound coil springs manufactured from an expandable heat sensitive material such as nickel-titanium; and self-expanding stents inserted in a compressed state and shaped in a zig-zag pattern.
Typically, the aforementioned stents are delivered intraluminally through a percutaneous incision through the femoral or renal arteries. A stent is mounted on the distal end of an elongated catheter, typically on the balloon portion of a catheter, and the catheter and stent are advanced intraluminally to the site where the stent is to be implanted. Typically with expandable stents, the balloon portion of the catheter is inflated to expand the stent radially outwardly into contact with the arterial wall, whereupon the stent undergoes plastic deformation and remains in an expanded state to hold open and support the artery.
With respect to self-expanding stents, typically a retractably sheath is positioned over the self-expanding stent which is mounted on the distal end of the catheter. Once the catheter has been advanced intraluminally to the site where the stent is to be implanted, the sheath is withdrawn thereby allowing the self-expanding stent to expand radially outwardly into contact with the arterial wall, thereby holding open and supporting the artery.
One of the problems associated with the prior art stents and catheter-delivery systems, is to removably attach the stent to the catheter""s distal end or the balloon portion of the catheter so that the stent does not dislodge or move axially on the catheter or balloon.
What has been needed and heretofore unavailable is a reliable catheter-delivery system on which the stent can be mounted and removably attached so that it does not move axially on the catheter either during delivery and advancement through the vascular system, or during implanting of the stent. The present invention satisfies this need.
The present invention is directed to a self-expanding stent delivery system in which a self-expanding stent is removably attached to a catheter so that the stent remains in position on the catheter until it is implanted. Unlike prior art stents, which may have a tendency to dislodge or move axially on the catheter shaft when the sheath is withdrawn or when the catheter is advanced through a tortuous vasculature, the present invention provides means for removably attaching the stent to the catheter so that it cannot move axially on the catheter shaft.
A catheter assembly for removably attaching an intravascular stent is provided in which an elongated catheter has an inner member and an outer member extending along a longitudinal axis wherein the inner member and the outer member have a coaxial configuration and are dimensioned for relative axial movement. A self-expanding stent, having an open lattice structure, and being biased toward an open configuration, is mounted within the outer member. The inner member is slidably positioned within the lumen of the stent, and then the inner member is heated until it conforms and fills the open lattice structure of the stent with attachment projections.
The present invention includes an inner member that is naturally pliable and deformable or is heat-deformable and formed from a polymeric material which when heated will fill the open lattice structure of the stent with attachment projections. The inner member can be formed from polymeric materials including polyurethanes, polyethylenes, polyethylterpthalate, and nylons.
In another embodiment of the invention, an elastomeric sleeve is attached to the distal end of the inner member. This stent is mounted in the distal end of the outer member and is biased outwardly against the outer member. The inner member distal end and its sleeve are positioned within the stent, and the sleeve is heated until it fills and forms attachment projections in the open lattice structure of the stent.
The invention also relates to the method of mounting the self-expanding stent on the delivery catheter. The delivery catheter includes an outer member and an inner member having relative axial movement and control handles for providing relative axial movement between the members. The self-expanding stent is positioned within the inner lumen of the outer member and the control handles are manipulated to slide the inner member distal end within the inner lumen of the self-expanding stent. Thereafter, heat is applied to the inner member distal end so that it conforms and fills the open lattice structure of the self-expanding stent with attachment projections, thereby removably attaching the self-expanding stent to the inner member distal end and preventing axial movement of the stent. The self-expanding stent remains biased radially outwardly and is retained from expanding by the outer member.
The invention also includes a method of implanting a self-expanding stent utilizing the catheter-delivery system described above. Using the catheter-delivery system, the stent is advanced through a patient""s vascular system until it is positioned at the site where the stent is to be implanted. The control handles are manipulated to simultaneously move the inner member axially in a distal direction and the outer member axially in a proximal direction. As the stent is exposed and no longer retained by the outer member, it will deploy by self-expanding radially outwardly into contact with the body lumen. The stent will not move axially on the catheter shaft as the inner member and the outer member are moved axially relative to one another, since the stent is removably attached to the inner member by attachment projections. After the stent is deployed, the catheter-delivery system is withdrawn from the patient.
One feature of the present invention is to permit the physician to partially deploy the stent, and if it is improperly positioned, the outer member can be moved axially to recapture the partially deployed stent so that the stent can be repositioned in the proper location. For example, the control handles can be manipulated to simultaneously move the inner member axially in the distal direction and the outer member axially in a proximal direction to begin to deploy the stent. Thereafter, if it is determined that the stent is being implanted at the wrong location in an artery, the control handles can be manipulated to simultaneously move the inner member axially in a proximal direction and the outer member axially in a distal direction to recapture the partially deployed stent so that it can be repositioned in the proper location in the artery. The stent is then implanted as described above.
Other features and advantages of the present invention will become more apparent from the following detailed description of the invention, when taken in conjunction with the accompanying exemplary drawings.